Isotope effects on the rotationally inelastic diffraction dynamics of hydrogen scattered from Cu(0 0 1)

We investigate the rotationally inelastic diffraction (RID) of D2(H2) scattered from Cu(0 0 1) and discuss how isotope effects influence the RID probabilities of D2(H2) by performing quantum dynamics calculations that include all six degrees of freedom of D2(H2). We show that the RID probabilities initially increase with increasing incident energies due to the activated nature of D2(H2) dissociation on Cu(0 0 1), which qualitatively agree with recent experimental RID peaks measured for D2/Cu(0 0 1). Furthermore, comparing the RID probabilities of D2 and H2, we observed strong isotope effects. Due to the small threshold energy of D2 for rotational excitation and diffraction, as compared to H2, the RID probabilities of D2 are larger than those of H2 in the low incident energy region. However with further increase in incident energies, the RID probabilities of D2 become smaller than those of H2. We conclude that this is a manifestation of the steering effect in the RID.